>For banks, the $91.2 billion in fees they earn on credit-card portfolios is now more than the interest they charge on the loans.
The fees are ridiculous. Profit margins at restaurants are often 3-5% (per Google). There is still a cost to handling cash, but if cash cost ~1% all-in, their profits would go up 20-30%, just like that, assuming consumption stayed the same.
Fast food venues didn't accept credit cards for a long time, but eventually found people spent more paying with a card than cash. A $300 TV and a $5 hamburger "feel" exactly the same with cards, which certainly doesn't help consumerism in the US.
As an example, when I pay my property taxes, I can either pay by sending a check in the mail, doing an electronic check (ACH transfer that takes 2-3 business days to clear) and paying $0.25, or pay a 2% transaction fee. Stamps are $0.50, eventually I'll need to reorder checks (at a cost), so I do the ACH transfer.